FAIRBANKS, Alaska  An increasing number of redpolls are dying off in the Fairbanks area this winter, baffling wildlife biologists. Experts had suspected the red-capped finches were dying of salmonellosis, but preliminary cultures did not confirm the presence of the bacteria.

Kimberlee Beckman, a wildlife veterinarian with the Alaska Department of Fish and Game, sent tissues from dead redpolls to the state public health lab last week. She received the results Friday. She also sent another sample to the Washington Animal Disease Diagnostic Lab and is awaiting results.

Beckmen said the next likely affliction to cause a similar die-off is a mycoplasma organism. But the dead redpolls she has seen do not have corresponding symptoms.

"I'm really very shocked it's not salmonella at this point," she said. "It should have been salmonella. I don't know what else it could be."

Whatever the culprit is, it's likely being passed from bird to bird at feeders, according to Beckman. She said bird enthusiasts should continue to take precautions as if the outbreak was salmonella.

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That includes cleaning feeders frequently and disposing of dead birds so that pets do not become infected.

The high number of redpolls this year increased the chances of an outbreak, said wildlife biologist John Wright. For several years in the late 1980s and early 1990s, the redpoll count went up and down before leveling off in the late 1990s.

This year, the red-capped finches arrived early and in full force. Usually not seen in the area until January or February, record numbers were being spotted as early as October. The Christmas Bird Count documented 8,231 redpolls in this year's annual tally, surpassing the previous record of 7,164 redpolls counted in 1997.

Wright estimated that less than 1 percent of the redpoll population has been affected by the undiagnosed malady.

Wright said there hasn't been a die-off this broad in the area since a salmonella outbreak 10 or 12 years ago. The U.S. Fish and Wildlife Service reported an outbreak of salmonellosis in pine siskins in the Juneau area last month.